1. Field of the Invention
This invention relates to ring forgings and, more particularly, to removing test specimens from the ring forgings.
2. Description of Related Art
Gas turbine engines, as well as many other products, incorporate many annular or cylindrical parts made from forgings or ring forgings. The forgings usually have a near net shape form and are machined to produce the part with final part dimensions and finishes. The forgings and parts are circumscribed about an axis of revolution about which they are usually symmetrical. These parts include rotating portions of rotors including disks or stationary casings and the like, including combustor liners.
Mechanical test specimens are made from the forging for mechanical testing for stress and strain capability as part of quality control of the forging process. The process of making and testing the specimen is a destructive test and so sacrificial forgings or test rings are formed integral with the forging. The test rings are made from wasted forging material that is not incorporated in the forged part. The test ring is cut off or otherwise separated from the forging. Arcuate sections of the test ring are cut from the test ring and machined into round bar test specimens of prescribed dimensions for use in subsequent mechanical testing. Test specimens are typically cylindrical, circumscribed about a specimen axis, and have a reduced section disposed between two grip sections. Test specimens may also be rectangular in cross section.
American National Standard Test Methods for Tension Testing of Metallic Materials have been established for making and using these types of test specimens and are described in American Association State Highway and Transportation Officials Standard AASHTO No. T68. These test methods cover the tension testing of metallic materials in any form at room temperature, specifically, the methods of determination of yield strength, yield point elongation, tensile strength, elongation, and reduction of area.
The test ring portion of the forging is a waste of forging material and adds to the cost of the forging and the process of forging and machining the forging. It is highly desirable to eliminate the test ring in the forging and forging process. In some cases entire forging rings are sacrificed.